Methods of selective deposition of heavily doped epitaxial SiGe

ABSTRACT

The invention generally teaches a method for depositing a silicon film or silicon germanium film on a substrate comprising placing the substrate within a process chamber and heating the substrate surface to a temperature in the range from about 600° C. to about 900° C. while maintaining a pressure in the range from about 0.1 Torr to about 200 Torr. A deposition gas is provided to the process chamber and includes SiH 4 , an optional germanium source gas, an etchant, a carrier gas and optionally at least one dopant gas. The silicon film or the silicon germanium film is selectively and epitaxially grown on the substrate. One embodiment teaches a method for depositing a silicon-containing film with an inert gas as the carrier gas. Methods may include the fabrication of electronic devices utilizing selective silicon germanium epitaxial films.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to the field ofsemiconductor manufacturing processes and devices, more particular, tomethods of depositing silicon-containing films forming semiconductordevices.

2. Description of the Related Art

As smaller transistors are manufactured, ultra shallow source/drainjunctions are becoming more challenging to produce. According to theInternational Technology Roadmap for Semiconductors (ITRS), junctiondepth is required to be less than 30 nm for sub-100 nm CMOS(complementary metal-oxide semiconductor) devices. Conventional dopingby implantation and annealing is less effective as the junction depthapproaches 10 nm. Doping by implantation requires a post-annealingprocess in order to activate dopants and post-annealing causes enhanceddopant diffusion into layers.

Recently, heavily-doped (about >10¹⁹ atoms/cm³), selective SiGe epitaxyhas become a useful material to deposit during formation of elevatedsource/drain and source/drain extension features. Source/drain extensionfeatures are manufactured by etching silicon to make a recessedsource/drain feature and subsequently filling the etched surface with aselectively grown SiGe epilayer. Selective epitaxy permits near completedopant activation with in-situ doping, so that the post annealingprocess is omitted. Therefore, junction depth can be defined accuratelyby silicon etching and selective epitaxy. On the other hand, the ultrashallow source/drain junction inevitably results in increased seriesresistance. Also, junction consumption during silicide formationincreases the series resistance even further. In order to compensate forjunction consumption, an elevated source/drain is epitaxially andselectively grown on the junction.

Selective Si epitaxial deposition and SiGe epitaxial deposition permitsgrowth of epilayers on Si moats with no growth on dielectric areas.Selective epitaxy can be used in semiconductor devices, such as withinelevated source/drains, source/drain extensions, contact plugs, and baselayer deposition of bipolar devices. Generally, a selective epitaxyprocess involves two reactions: deposition and etching. They occursimultaneously with relatively different reaction rates on Si and ondielectric surface. A selective process window results in depositiononly on Si surfaces by changing the concentration of an etchant gas(e.g., HCl). A popular process to perform selective, epitaxy depositionis to use dichlorosilane (SiH₂Cl₂) as a silicon source, germane (GeH₄)as a germanium source, HCl as an etchant to provide selectivity duringthe deposition and hydrogen (H₂) as a carrier gas.

Although SiGe epitaxial deposition is suitable for small dimensions,this approach does not readily prepare doped SiGe, since the dopantsreact with HCl. The process development of heavily boron doped (e.g.,higher than 5×10¹⁹ cm⁻³) selective SiGe epitaxy is a much morecomplicated task because boron doping makes the process window forselective deposition narrow. Generally, when more boron concentration(e.g., B₂H₆) is added to the flow, a higher HCl concentration isnecessary to achieve selectivity due to the increase growth rate ofdeposited film(s) on any dielectric areas. This higher HCl flow rateproportionally reduces boron incorporation into the epilayers presumablybecause the B—Cl bond is stronger than Ge—Cl and Si—Cl bonds.

Therefore, there is a need to have a process for selectively andepitaxially depositing silicon and silicon compounds with an enricheddopant concentration. Furthermore, the process must maintain a highgrowth of the deposited material. Also, the process must have lessdependency on germanium and boron concentrations in the silicon compoundin relation to an etchant flow rate.

SUMMARY OF THE INVENTION

In one embodiment, the invention generally provides a method ofdepositing a silicon germanium film on a substrate comprising placingthe substrate within a process chamber and heating the substrate surfaceto a temperature in a range from about 500° C. to about 900° C. whilemaintaining a pressure in a range from about 0.1 Torr to about 200 Torr.A deposition gas is provided to the process chamber and includes SiH₄,GeH₄, HCl, a carrier gas and at least one dopant gas, such as diborane,arsine or phosphine. A doped silicon germanium film is epitaxially grownon the substrate.

In another embodiment, the invention generally provides a selectiveepitaxial method for growing a doped silicon germanium film on asubstrate comprising placing the substrate within a process chamber at apressure in a range from about 0.1 Torr to about 200 Torr and heatingthe substrate surface to a temperature in a range from about 500° C. toabout 900° C. A deposition gas is provided to the process chamber andincludes SiH₄, a germanium source, an etchant source, a carrier gas andat least one dopant gas. The silicon germanium film is grown with adopant concentration in a range from about 1×10²⁰ atoms/cm³ to about2.5×10²¹ atoms/cm³.

In another embodiment, the invention generally provides a selectiveepitaxial method for growing a silicon-containing film on a substratecomprising placing the substrate within a process chamber at a pressurein a range from about 0.1 Torr to about 200 Torr and heating thesubstrate surface to a temperature in a range from about 500° C. toabout 900° C. A deposition gas is provided to the process chamber andincludes SiH₄, HCl and a carrier. The silicon-containing film is grownat a rate between about 50 Å/min and about 600 Å/min.

In another embodiment, the invention generally provides a selectiveepitaxial method for growing a silicon-containing film on a substratecomprising placing the substrate within a process chamber at a pressurein a range from about 0.1 Torr to about 200 Torr, heating the substrateto a temperature in a range from about 500° C. to about 900° C.,providing a deposition gas comprising Cl₂SiH₂, HCl and a carrier gas anddepositing a silicon-containing layer on the substrate. The methodfurther comprises providing a second deposition gas comprising SiH₄, HCland a second carrier gas and depositing a second silicon-containinglayer on the silicon-containing layer.

In another embodiment, the invention generally provides a method ofselectively depositing a silicon-containing film on a substratecomprising placing the substrate within a process chamber, heating thesubstrate to a temperature in a range from about 500° C. to about 900°C. and maintaining a pressure in a range from about 0.1 Torr to about200 Torr. The method further comprises providing a deposition gascomprising a silicon-containing gas, a germanium source, HCl, at leastone dopant gas and a carrier gas selected from the group consisting ofN₂, Ar, He and combinations thereof and depositing thesilicon-containing film epitaxially on the substrate

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A–C show several devices with epitaxially depositedsilicon-containing layer; and

FIGS. 2A–F show schematic illustrations of fabrication techniques for asource/drain extension device within a MOSFET.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention provides a process to epitaxially deposit siliconcontaining compounds during the manufacture of various devicestructures. In some embodiments, the process utilizes the siliconprecursor silane (SiH₄) during the deposition of silicon compounds.While past techniques usually have used silicon precursors such asdichlorosilane, tetrachlorosilane or hexachlorodisilane, processes ofthe present invention teach the utilization of silane as a precursor.The use of silane has been found to deposit silicon containing filmsmore quickly than that of dichlorosilane. Also, the use of silane duringthese processes provides a higher degree of control for dopantconcentrations within the film and increased deposition rate.

Embodiments of the present invention teach processes to grow films ofselective, epitaxial silicon compounds. Selective silicon containingfilm growth generally is conducted when the substrate or surfaceincludes more than one material, such as exposed single crystallinesilicon surface areas and features that are covered with dielectricmaterial, such as oxide or nitride layers. Usually, these features aredielectric material. Selective epitaxial growth to the crystalline,silicon surface is achieved while the feature is left bare, generally,with the utilization of an etchant (e.g., HCl). The etchant removesamorphous silicon or polysilicon growth from features quicker than theetchant removes crystalline silicon growth from the substrate, thusselective epitaxial growth is achieved.

Carrier gases are used throughout the processes and include H₂, Ar, N₂,He and combinations thereof. In one example, H₂ is used as a carriergas. In another example N₂ is used as a carrier gas. In one embodiment,a carrier gas during an epitaxial deposition process is conducted withneither H₂ nor atomic hydrogen. However, an inert gas is used as acarrier gas, such as N₂, Ar, He and combinations thereof. Carrier gasesmay be combined in various ratios during some embodiments of theprocess.

In one embodiment, a carrier gas includes N₂ and/or Ar to maintainavailable sites on the silicon compound film. The presence of hydrogenon the silicon compound surface limits the number of available sites(i.e., passivates) for Si or SiGe to grow when an abundance of H₂ isused as a carrier gas. Consequently, a passivated surface limits thegrowth rate at a given temperature, particularly at lower temperatures(e.g., <650° C.). Therefore, a carrier gas of N₂ and/or Ar may be usedduring a process at lower temperature and reduce the thermal budgetwithout sacrificing growth rate.

In one embodiment of the invention, a silicon compound film isepitaxially grown as a Si film. A substrate (e.g., 300 mm OD) containinga semiconductor feature is placed into the process chamber. During thisdeposition technique, silicon precursor (e.g., silane) is flownconcurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂) and an etchant (e.g., HCl). The flow rate of the silane is inthe range from about 5 sccm to about 500 sccm. The flow rate of thecarrier gas is from about 1,000 sccm to about 60,000 sccm. The flow rateof the etchant is from about 5 sccm to about 1,000 sccm. The processchamber is maintained with a pressure from about 0.1 Torr to about 200Torr, preferably at about 15 Torr. The substrate is kept at atemperature in the range from about 500° C. to about 1,000° C.,preferably from about 600° C. to about 900° C. for example, from 600° C.to 750° C., for another example from 650° C. to 800° C. The mixture ofreagents is thermally driven to react and epitaxially depositcrystalline silicon. The HCl etches any deposited amorphous silicon orpolycrystalline silicon from dielectric features upon the surface of thesubstrate. The process is conducted to form the deposited siliconcompound with a thickness in a range from about 100 Å to about 3,000 Åand at a deposition rate between about 50 Å/min and about 600 Å/min,preferably at about 150 Å/min. In one embodiment, the silicon compoundhas a thickness greater than 500 Å, such as about 1,000 Å.

Etchants are utilized to control the areas on the device to be free ofdeposited silicon compound. Etchants that are useful during depositionprocesses of the invention include HCl, HF, HBr, Si₂Cl₆, SiCl₄, Cl₂SiH₂,CCl₄, Cl₂ and combinations thereof. Other silicon precursors, besidessilane, that are useful while depositing silicon compounds includehigher silanes and organosilanes. Higher silanes include the compoundswith the empirical formula Si_(x)H_((2X+2)), such as disilane (Si₂H₆),trisilane (Si₃H₈) and tetrasilane (Si₄H₁₀), as well as others.Organosilanes include compounds with the empirical formulaR_(y)Si_(x)H_((2x+2−y)), where R=methyl, ethyl, propyl or butyl, such asmethylsilane ((CH₃)SiH₃), dimethylsilane ((CH₃)₂SiH₂), ethylsilane((CH₃CH₂)SiH₃), methyldisilane ((CH₃)Si₂H₅), dimethyldisilane((CH₃)₂Si₂H₄) and hexamethyldisilane ((CH₃)₆Si₂). Organosilane compoundshave been found to be advantageous silicon sources and carbon sourcesduring embodiments of the present invention to incorporate carbon in todeposited silicon compound.

In another embodiment of the invention, a silicon compound film isepitaxially grown as a SiGe film. A substrate (e.g., 300 mm OD)containing a semiconductor feature is placed into the process chamber.During this deposition technique, silicon precursor (e.g., silane) isflown concurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂), a germanium source (e.g., GeH₄) and an etchant (e.g., HCl).The flow rate of the silane is in the range from about 5 sccm to about500 sccm. The flow rate of the carrier gas is from about 1,000 sccm toabout 60,000 sccm. The flow rate of the germanium source is from about0.1 sccm to about 10 sccm. The flow rate of the etchant is from about 5sccm to about 1,000 sccm. The process chamber is maintained with apressure from about 0.1 Torr to about 200 Torr, preferably at about 15Torr. The substrate is kept at a temperature in the range from about500° C. to about 1,000° C., preferably from about 700° C. to about 900°C. The reagent mixture is thermally driven to react and epitaxiallydeposit a silicon compound, namely a silicon germanium film. The HCletches any deposited amorphous SiGe compounds from dielectric featuresupon the surface of the substrate. The process is conducted to form thedeposited SiGe compound with a thickness in a range from about 100 Å toabout 3,000 Å and at a deposition rate between about 50 Å/min and about300 Å/min, preferably at about 150 Å/min. The germanium concentration isin the range from about 1 atomic percent to about 30 atomic percent ofthe SiGe compound, preferably at about 20 atomic percent.

Other germanium sources or precursors, besides germane, that are usefulwhile depositing silicon compounds include higher germanes andorganogermanes. Higher germanes include the compounds with the empiricalformula Ge_(x)H_((2x+2)), such as digermane (Ge₂H₆), trigermane (Ge₃H₈)and tetragermane (Ge₄H₁₀), as well as others. Organogermanes includecompounds with the empirical formula R_(y)Ge_(x)H_((2x+2−y)), whereR=methyl, ethyl, propyl or butyl, such as methylgermane ((CH₃)GeH₃),dimethylgermane ((CH₃)₂GeH₂), ethylgermane ((CH₃CH₂)GeH₃),methyldigermane ((CH₃)Ge₂H₅), dimethyldigermane ((CH₃)₂Ge₂H₄) andhexamethyldigermane ((CH₃)₆Ge₂). Germanes and organogermane compoundshave been found to be an advantageous germanium sources and carbonsources during embodiments of the present invention to incorporategermanium and carbon in to the deposited silicon compounds, namely SiGeand SiGeC compounds.

In one embodiment of the invention, a silicon compound film isepitaxially grown as a doped Si film. A substrate (e.g., 300 mm OD)containing a semiconductor feature is placed into the process chamber.During this deposition technique, silicon precursor (e.g., silane) isflown concurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂), a dopant (e.g., B₂H₆) and an etchant (e.g., HCl). The flowrate of the silane is in the range from about 5 sccm to about 500 sccm.The flow rate of the carrier gas is from about 1,000 sccm to about60,000 sccm. The flow rate of the dopant is from about 0.01 sccm toabout 3 sccm. The flow rate of the etchant is from about 5 sccm to about1,000 sccm. The process chamber is maintained with a pressure from about0.1 Torr to about 200 Torr, preferably at about 15 Torr. The substrateis kept at a temperature in the range from about 500° C. to about 1,000°C., preferably from about 700° C. to about 900° C. The mixture ofreagents is thermally driven to react and epitaxially deposit dopedsilicon films. The HCl etches any deposited amorphous silicon orpolycrystalline silicon from dielectric features upon the surface of thesubstrate. The process is conducted to form the deposited, doped siliconcompound with a thickness in a range from about 100 Å to about 3,000 Åand at a deposition rate between about 50 Å/min and about 600 Å/min,preferably at about 150 Å/min.

Dopants provide the deposited silicon compounds with various conductivecharacteristics, such as directional electron flow in a controlled anddesired pathway required by the electronic device. Films of the siliconcompounds are doped with particular dopants to achieve the desiredconductive characteristic. In one embodiment, the silicon compound isdoped p-type, such as by using diborane to add boron at a concentrationin the range from about 10¹⁵ atoms/cm³ to about 10²¹ atoms/cm³. In oneembodiment, the p-type dopant has a concentration of at least 5×10¹⁹atoms/cm³. In another embodiment, the p-type dopant is in the range fromabout 1×10²⁰ atoms/cm³ to about 2.5×10²¹ atoms/cm³. In anotherembodiment, the silicon compound is doped n-type, such as withphosphorus and/or arsenic to a concentration in the range from about10¹⁵ atoms/cm³ to about 10²¹ atoms/cm³.

Besides diborane, other boron containing dopants include boranes andorganoboranes. Boranes include borane, triborane, tetraborane andpentaborane, while alkylboranes include compounds with the empiricalformula R_(x)BH_((3−x)), where R=methyl, ethyl, propyl or butyl and x=0,1, 2 or 3. Alkylboranes include trimethylborane ((CH₃)₃B),dimethylborane ((CH₃)₂BH), triethylborane ((CH₃CH₂)₃B) and diethylborane((CH₃CH₂)₂BH). Dopants also include arsine (AsH₃), phosphine (PH₃) andalkylphosphines, such as with the empirical formula R_(x)PH_((3−x)),where R=methyl, ethyl, propyl or butyl and x=0, 1, 2 or 3.Alkylphosphines include trimethylphosphine ((CH₃)₃P), dimethylphosphine((CH₃)₂PH), triethylphosphine ((CH₃CH₂)₃P) and diethylphosphine((CH₃CH₂)₂PH).

In another embodiment of the invention, a silicon compound film isepitaxially grown to produce a doped SiGe. A substrate (e.g., 300 mm OD)containing a semiconductor feature is placed into the process chamber.During this deposition technique, silicon precursor (e.g., silane) isflown concurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂), a germanium source (e.g., GeH₄), a dopant (e.g., B₂H₆) andan etchant (e.g., HCl). The flow rate of the silane is in the range fromabout 5 sccm to about 500 sccm. The flow rate of the carrier gas is fromabout 1,000 sccm to about 60,000 sccm. The flow rate of the germaniumsource is from about 0.1 sccm to about 10 sccm. The flow rate of thedopant is from about 0.01 sccm to about 3 sccm. The flow rate of theetchant is from about 5 sccm to about 1,000 sccm. The process chamber ismaintained with a pressure from about 0.1 Torr to about 200 Torr,preferably at about 15 Torr. The substrate is kept at a temperature inthe range from about 500° C. to about 1,000° C., preferably from about700° C. to about 900° C. The reagent mixture is thermally driven toreact and epitaxially deposit a silicon compound, namely a silicongermanium film. The HCl etches any deposited amorphous SiGe fromfeatures upon the surface of the substrate. The process is conducted toform the doped SiGe compound with a thickness in a range from about 100Å to about 3,000 Å and at a rate between about 50 Å/min and about 600Å/min, preferably at about 150 Å/min. The germanium concentration is inthe range from about 1 atomic percent to about 30 atomic percent of theSiGe compound, preferably at about 20 atomic percent. The boronconcentration is in the range from about 1×10²⁰ atoms/cm³ to about2.5×10²¹ atoms/cm³ of the SiGe compound, preferably at about 2×10²⁰atoms/cm³.

In another embodiment of the invention, a silicon compound film isepitaxially grown as a SiGeC film. A substrate (e.g., 300 mm OD)containing a semiconductor feature is placed into the process chamber.During this deposition technique, silicon precursor (e.g., silane) isflown concurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂), a germanium source (e.g., GeH₄), a carbon source (e.g.,CH₃SiH₃) and an etchant (e.g., HCl). The flow rate of the silane is inthe range from about 5 sccm to about 500 sccm. The flow rate of thecarrier gas is from about 1,000 sccm to about 60,000 sccm. The flow rateof the germanium source is from about 0.1 sccm to about 10 sccm. Theflow rate of the carbon source is from about 0.1 sccm to about 50 sccm.The flow rate of the etchant is from about 5 sccm to about 1,000 sccm.The process chamber is maintained with a pressure from about 0.1 Torr toabout 200 Torr, preferably at about 15 Torr. The substrate is kept at atemperature in the range from about 500° C. to about 1,000° C.,preferably from about 500° C. to about 700° C. The reagent mixture isthermally driven to react and epitaxially deposit a silicon compound,namely a silicon germanium carbon film. The HCl etches any depositedamorphous or polycrystalline SiGeC compounds from dielectric featuresupon the surface of the substrate. The process is conducted to form thedeposited SiGeC compound with a thickness in a range from about 100 Å toabout 3,000 Å and at a deposition rate between about 50 Å/min and about600 Å/min, preferably at about 150 Å/min. The germanium concentration isin the range from about 1 atomic percent to about 30 atomic percent ofthe SiGeC compound, preferably at about 20 atomic percent. The carbonconcentration is in the range from about 0.1 atomic percent to about 5atomic percent, preferably at about 2 atomic percent of the SiGeCcompound.

Other carbon sources or precursors, besides ethylene or methane, areuseful while depositing silicon compounds and include alkyls, alkenesand alkynes of ethyl, propyl and butyl. Such carbon sources includeethyne (C₂H₂), propane (C₃H₈), propene (C₃H₆), butyne (C₄H₆), as well asothers. Other carbon sources include organosilane compounds, asdescribed in relation to silicon sources.

In another embodiment of the invention, a silicon compound film isepitaxially grown as a doped-SiGeC film. A substrate (e.g., 300 mm OD)containing a semiconductor feature is placed into the process chamber.During this deposition technique, silicon precursor (e.g., silane) isflown concurrently into the process chamber with a carrier gas (e.g., H₂and/or N₂), a germanium source (e.g., GeH₄), a carbon source (e.g.,CH₃SiH₃), a dopant (e.g., B₂H₆) and an etchant (e.g., HCl). The flowrate of the silane is in the range from about 5 sccm to about 500 sccm.The flow rate of the carrier gas is from about 1,000 sccm to about60,000 sccm. The flow rate of the germanium source is from about 0.1sccm to about 10 sccm. The flow rate of the carbon source is from about0.1 sccm to about 50 sccm. The flow rate of the dopant is from about0.01 sccm to about 3 sccm. The flow rate of the etchant is from about 5sccm to about 1,000 sccm. The process chamber is maintained with apressure from about 0.1 Torr to about 200 Torr, preferably at about 15Torr. The substrate is kept at a temperature in the range from about500° C. to about 1,000° C., preferably from about 500° C. to about 700°C. The reagent mixture is thermally driven to react and epitaxiallydeposit a silicon compound, namely a doped silicon germanium carbonfilm. The HCl etches any deposited amorphous or polycrystalline SiGeCcompounds from dielectric features upon the surface of the substrate.The process is conducted to form the deposited SiGeC compound with athickness in a range from about 100 Å to about 3,000 Å and at adeposition rate between about 50 Å/min and about 600 Å/min, preferablyat about 150 Å/min. The germanium concentration is in the range fromabout 1 atomic percent to about 30 atomic percent of the SiGeC compound,preferably at about 20 atomic percent. The carbon concentration is inthe range from about 0.1 atomic percent to about 5 atomic percent of theSiGeC compound, preferably at about 2 atomic percent. The boronconcentration is in the range from about 1×10²⁰ atoms/cm³ to about2.5×10²¹ atoms/cm³ of the SiGe compound, preferably at about 2×10²⁰atoms/cm³.

In another embodiment of the invention, a second silicon compound filmis epitaxially grown as a SiGe film by using dichlorosilane,subsequently to depositing any of the silicon compounds as describedabove via silane as a silicon source. A substrate (e.g., 300 mm OD)containing any of the above described silicon containing compounds isplaced into the process chamber. During this deposition technique,silicon precursor (e.g., Cl₂SiH₂) is flown concurrently into the processchamber with a carrier gas (e.g., H₂ and/or N₂), a germanium source(e.g., GeH₄) and an etchant (e.g., HCl). The flow rate of thedichlorosilane is in the range from about 5 sccm to about 500 sccm. Theflow rate of the carrier gas is from about 1,000 sccm to about 60,000sccm. The flow rate of the germanium source is from about 0.1 sccm toabout 10 sccm. The flow rate of the etchant is from about 5 sccm toabout 1,000 sccm. The process chamber is maintained with a pressure fromabout 0.1 Torr to about 200 Torr, preferably at about 15 Torr. Thesubstrate is kept at a temperature in the range from about 500° C. toabout 1,000° C., preferably from about 700° C. to about 900° C. Thereagent mixture is thermally driven to react and epitaxially deposit asecond silicon compound, namely a silicon germanium film. The HCl etchesany deposited amorphous or polycrystalline SiGe compounds from anydielectric features upon the surface of the substrate. The process isconducted to form the deposited SiGe compound with a thickness in arange from about 100 Å to about 3,000 Å and at a deposition rate betweenabout 10 Å/min and about 100 Å/min, preferably at about 50 Å/min. Thegermanium concentration is in the range from about 1 atomic percent toabout 30 atomic percent of the SiGe compound, preferably at about 20atomic percent. This embodiment describes a process to deposit a SiGefilm, though substitution of silane with dichlorosilane to any of thepreviously described embodiments will produce a second siliconcontaining film. In another embodiment, a third silicon containing layeris deposited using any of the silane based process discussed above.

Therefore, in one embodiment, a silicon compound laminate film may bedeposited in sequential layers of silicon compound by altering thesilicon precursor between silane and dichlorosilane. In one example, alaminate film of about 2,000 Å is formed by depositing four siliconcompound layers (each of about 500 Å), such that the first and thirdlayers are deposited using dichlorosilane and the second and fourthlayers are deposited using silane. In another aspect of a laminate film,the first and third layers are deposited using silane and the second andfourth layers are deposited using dichlorosilane. The thickness of eachlayer is independent from each other; therefore, a laminate film mayhave various thicknesses of the silicon compound layers.

In one embodiment, dichlorosilane is used to deposit the siliconcompound layer when the previous layer contains surface islands (e.g.,contamination or irregularity to film). A process incorporatingdichlorosilane may be less sensitive to the surface islands whiledepositing the silicon compound layer over the previous layer. The useof dichlorosilane as the silicon source has a high horizontal or lateralgrowth rate relative to the use of silane. Once the surface island iscovered and the silicon compound layer has a consistent surface,dichlorosilane is replaced with silane and deposition of the siliconcompound layer is continued.

Embodiments of the invention teach processes to deposit siliconcompounds on many substrates and surfaces. Substrates on whichembodiments of the invention may be useful include, but are not limitedto semiconductor wafers, such as crystalline silicon (e.g., Si<100> andSi<111>), silicon oxide, silicon germanium, doped or undoped wafers andpatterned or non-patterned wafers. Substrates have a variety ofgeometries (e.g., round, square and rectangular) and sizes (e.g., 200 mmOD, 300 mm OD). Surfaces and./or substrates include wafers, films,layers and materials with dielectric, conductive and barrier propertiesand include polysilicon, silicon on insulators (SOI), strained andunstrained lattices. Pretreatment of surfaces includes polishing,etching, reduction, oxidation, hydroxylation, annealing and baking. Inone embodiment, wafers are dipped into a 1% HF solution, dried and bakedin a hydrogen atmosphere at 800° C.

In one embodiment, silicon compounds include a germanium concentrationwithin the range from about O atomic percent to about 95 atomic percent.In another embodiment, a germanium concentration is within the rangefrom about 1 atomic percent to about 30 atomic percent, preferably fromabout 15 atomic percent to about 25 atomic percent and more preferablyat about 20 atomic percent. Silicon compounds also include a carbonconcentration within the range from about 0 atomic percent to about 5atomic percent. In other aspects, a carbon concentration is within therange from about 200 ppm to about 2 atomic percent.

The silicon compound films of germanium and/or carbon are produced byvarious processes of the invention and can have consistent, sporadic orgraded elemental concentrations. Graded silicon germanium films aredisclosed in U.S. patent applications 20020174826 and 20020174827assigned to Applied Material, Inc., and are incorporated herein byreference in entirety for the purpose of describing methods ofdepositing graded silicon compound films. In one embodiment, silane anda germanium source (e.g., GeH₄) are used to deposit silicon germaniumcontaining films. In this embodiment, the ratio of silane and germaniumsource can be varied in order to provide control of the elementalconcentrations while growing graded films. In another embodiment, silaneand a carbon source (e.g., CH₃SiH₃) are used to deposit silicon carboncontaining films. The ratio of silane and carbon source can be varied inorder to provide control of the elemental concentration while growinghomogenous or graded films. In another embodiment, silane, a germaniumsource (e.g., GeH₄) and a carbon source (e.g., CH₃SiH₃) are used todeposit silicon germanium carbon containing films. The ratio of silane,germanium and carbon source can be varied in order to provide control ofthe elemental concentration while growing homogenous or graded films.

In processes of the invention, silicon compound films are grown bychemical vapor deposition (CVD) processes, wherein CVD processes includeatomic layer deposition (ALD) processes and/or atomic layer epitaxy(ALE) processes. Chemical vapor deposition includes the use of manytechniques, such as plasma-assisted CVD (PA-CVD), atomic layer CVD(ALCVD), organometallic or metalorganic CVD (OMCVD or MOCVD),laser-assisted CVD (LA-CVD), ultraviolet CVD (UV-CVD), hot-wire (HWCVD),reduced-pressure CVD (RP-CVD), ultra-high vacuum CVD (UHV-CVD) andothers. In one embodiment, the preferred process of the presentinvention is to use thermal CVD to epitaxially grow or deposit thesilicon compound, whereas the silicon compound includes silicon, SiGe,SiC, SiGeC, doped variants thereof and combinations thereof.

The processes of the invention can be carried out in equipment known inthe art of ALE, CVD and ALD. The apparatus brings the sources intocontact with a heated substrate on which the silicon compound films aregrown. The processes can operate at a range of pressures from about 1mTorr to about 2,300 Torr, preferably between about 0.1 Torr and about200 Torr. Hardware that can be used to deposit silicon-containing filmsincludes the Epi Centura® system and the Poly Gen® system available fromApplied Materials, Inc., located in Santa Clara, Calif. An ALD apparatusis disclosed in U.S. patent application 20030079686, assigned to AppliedMaterial, Inc., and entitled “Gas Delivery Apparatus and Methods forALD”, and is incorporated herein by reference in entirety for thepurpose of describing the apparatus. Other apparatuses include batch,high-temperature furnaces, as known in the art.

The processes are extremely useful while depositing silicon compoundlayers in Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) andbipolar transistors as depicted in FIGS. 1A–1C. Herein, siliconcompounds are the deposited layers or films and include Si, SiGe, SiC,SiGeC, doped variants thereof and combinations thereof, epitaxiallygrown during the processes of the present invention. The siliconcompounds include strained or unstrained layers within the films.

FIGS. 1A–1B show the epitaxially grown silicon compound on a MOSFET. Thesilicon compound is deposited to the source/drain features of thedevice. The silicon compound adheres and grows from the crystal latticeof the underlying layer and maintains this arrangement as the siliconcompound grows with thickness. In one embodiment, FIG. 1A demonstratesthe silicon compound deposited as a source/drain extension source, whilein another embodiment, FIG. 1B shows the silicon compound deposited asan elevated source/drain (ESD).

The source/drain layer 12 is formed by ion implantation of the substrate10. Generally, the substrate 10 is doped n-type while the source/drainlayer 12 is doped p-type. Silicon compound layer 14 is epitaxially grownto the source/drain layer 12 by the various embodiments of the presentinvention. A gate oxide layer 18 bridges the either the segmentedsilicon compound layer 14 (FIG. 1A) or the segmented source/drain layer12 (FIG. 1B). Generally, gate oxide layer 18 is composed of silicondioxide, silicon oxynitride or tantalum oxide. Partially encompassingthe gate oxide layer 18 is a spacer 16, which is usually an isolationmaterial such as a nitride/oxide stack (e.g., Si₃N₄/SiO₂/Si₃N₄). Alsowithin the spacer 16 is off-set layers 20 (e.g., Si₃N₄) and the gatelayer 22 (e.g., W or Ni).

In another embodiment, FIG. 1C depicts the deposited silicon compoundlayer 34 as a base layer of a bipolar transistor. The silicon compoundlayer 34 is epitaxially grown with the various embodiments of theinvention. The silicon compound layer 34 is deposited to an n-typecollector layer 32 previously deposited to substrate 30. The transistorfurther includes isolation layer 33 (e.g., SiO₂ or Si₃N₄), contact layer36 (e.g., heavily doped poly-Si), off-set layer 38 (e.g., Si₃N₄) and asecond isolation layer 40 (e.g., SiO₂ or Si₃N₄).

In one embodiment, as depicted in FIGS. 2A–2F, a source/drain extensionis formed within a MOSFET wherein the silicon compound layers areepitaxially and selectively deposited on the surface of the substrate.FIG. 2A depicts a source/drain layer 132 formed by implanting ions intothe surface of a substrate 130. The segments of source/drain layer 132are bridged by the gate 136 formed within off-set layer 134. A portionof the source/drain layer is etched and wet-cleaned, to produce a recess138, as in FIG. 2B.

FIG. 2C illustrates several embodiments of the present invention, inwhich silicon compound layers 140 (epitaxial) and 142 (polycrystalline)are selectively deposited. Silicon compound layers 140 and 142 aredeposited simultaneously without depositing on the off-set layer 134.Silicon compound layers 140 and 142 are generally doped SiGe containinglayers with a germanium concentration at about 1 atomic percent to about30 atomic percent, preferably at about 20 atomic percent and a dopant(e.g., B, As or P) concentration from about 1×10²⁰ atoms/cm³ to about2.5×10²¹ atoms/cm³, preferably at about 2×10²⁰ atoms/cm³. During thenext step, FIG. 2D shows the nitride spacer 144 (e.g., Si₃N₄) depositedto the off-set layer 134.

FIG. 2E depicts another embodiment of the present invention, in which asilicon compound is epitaxially and selectively deposited as siliconcompound layer 148. Silicon compound layer 148 is deposited on layer 140(doped-SiGe). Polysilicon layer 146 is deposited on the silicon compoundlayer 142 (doped-SiGe).

In the next step shown in FIG. 2F, a metal layer 154 is deposited overthe features and the device is annealed. The metal layer 154 includescobalt, nickel or titanium, among other metals. During the annealingprocess, polysilicon layer 146 and silicon compound layer 148 areconverted to metal silicide layers, 150 and 152, respectively. That is,when cobalt is deposited as metal layer 154, then metal silicide layers150 and 152 are cobalt silicide.

The silicon compound is heavily doped with the in-situ dopants.Therefore, annealing steps of the prior art are omitted and the overallthroughput is shorter. An increase of carrier mobility along the channeland subsequent drive current is achieved with the optional addition ofgermanium and/or carbon into the silicon compound layer. Selectivelygrown epilayers of the silicon compound above the gate oxide level cancompensate junction consumption during the silicidation, which canrelieve concerns of high series resistance of ultra shallow junctions.These two applications can be implemented together as well as solely forCMOS device fabrication.

Silicon compounds are utilized within embodiments of the processes todeposit silicon compounds films used for Bipolar (e.g., base, emitter,collector, emitter contact), BiCMOS (e.g., base, emitter, collector,emitter contact) and CMOS (e.g., channel, source/drain, source/drainextension, elevated source/drain, substrate, strained silicon, siliconon insulator and contact plug). Other embodiments of processes teach thegrowth of silicon compounds films that can be used as gate, basecontact, collector contact, emitter contact, elevated source/drain andother uses.

EXAMPLE 1 Boron Doped Silicon Germanium Deposition

A substrate, Si<100>, (e.g., 300 mm OD) was employed to investigateselective, monocrystalline film growth by CVD. A dielectric featureexisted on the surface of the wafer. The wafer was prepared bysubjecting to a 1% HF dip for 45 seconds. The wafer was loaded into thedeposition chamber (Epi Centura® chamber) and baked in a hydrogenatmosphere at 800° C. for 60 seconds to remove native oxide. A flow ofcarrier gas, hydrogen, was directed towards the substrate and the sourcecompounds were added to the carrier flow. Silane (100 sccm) and germane(6 sccm) were added to the chamber at 15 Torr and 725° C. Hydrogenchloride was delivered with a flow rate of 460 sccm. Diborane wasdelivered with a flow rate of 1 sccm. The substrate was maintained at725° C. Deposition was carried out for 5 minutes to form a 500 Å SiGefilm with a germanium concentration of 21 atomic percent and the boronconcentration was 2.0×10²⁰ cm⁻³.

EXAMPLE 2 Phosphorus Doped Silicon Germanium Deposition

A substrate was prepared as in Example 1. The wafer was loaded into thedeposition chamber (Epi Centura® chamber) and baked in a hydrogenatmosphere at 800° C. for 60 seconds to remove native oxide. A flow ofcarrier gas, hydrogen, was directed towards the substrate and the sourcecompounds were added to the carrier flow. Silane (100 sccm) and germane(4 sccm) were added to the chamber at 15 Torr and 725° C. Hydrogenchloride was delivered with a flow rate of 250 sccm. Phosphine wasdelivered to the chamber with a flow rate of 1 sccm. The substrate wasmaintained at 725° C. Deposition was carried out for 5 minutes to form a500 Å SiGe film with a germanium concentration of 20 atomic percent andthe phosphorus concentration was 1.6×10²⁰ cm⁻³.

EXAMPLE 3 Boron Doped Silicon Germanium Deposition with SequentialCl₂SiH₂ and SiH₄ Flows

The substrates were prepared as in Example 1. The wafer was loaded intothe deposition chamber (Epi Centura® chamber) and baked in a hydrogenatmosphere at 800° C. for 60 seconds to remove native oxide. A flow ofcarrier gas, hydrogen, was directed towards the substrate and the sourcecompounds were added to the carrier flow. Dichlorosilane (100 sccm),germane (2.8 sccm), and diborane (0.3 sccm) were added to the chamber at15 Torr and 725° C. Hydrogen chloride was delivered with a flow rate of190 sccm. The substrate was maintained at 725° C. Deposition wasconducted for 72 seconds to form a first layer of silicon compound witha thickness of 50 Å. On top of the first layer, a subsequent epitaxiallayer (i.e., a second layer of silicon compound) was deposited usingsilane (100 sccm), germane (6 sccm), hydrogen chloride (460 sccm) anddiborane (1 sccm). The chamber pressure and temperature remainedconstant (15 Torr and 725° C.) and the deposition was conducted for 144seconds to form 250 Å layer of the second layer.

EXAMPLES 4 Boron Doped Silicon Germanium Deposition with SequentialUsing SiH₄ and Cl₂SiH₂

The substrates were prepared as in Example 1. The wafer was loaded intothe deposition chamber (Epi Centura® chamber) and baked in a hydrogenatmosphere at 800° C. for 60 seconds to remove native oxide. A flow ofcarrier gas, hydrogen, was directed towards the substrate and the sourcecompounds were added to the carrier flow. Silane (100 sccm), germane (6sccm), and diborane (1 sccm) were added to the chamber at 15 Torr and725° C. Hydrogen chloride was delivered with a flow rate of 460 sccm.The substrate was maintained at 725° C. Deposition was conducted for 144seconds to form a first layer of silicon compound with a thickness of250 Å. On top of the first layer, a second layer of silicon compound wassequentially deposited using dichlorosilane (100 sccm), germane (2.8sccm), hydrogen chloride (190 sccm) and diborane (0.3 sccm). The chamberpressure and temperature remained constant (15 Torr and 725° C.) wasconducted for 72 seconds to form additional 50 Å layer.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for depositing a silicon germanium film on a substratecomprising: providing a substrate within a process chamber; heating thesubstrate to a temperature within a range from about 500° C. to about900° C.; exposing the substrate to a first deposition gas comprisingsilane, germanium, a carbon source, hydrogen chloride, a carrier gas,and at least one dopant gas to epitaxially and selectively deposit afirst silicon germanium material on the substrate, wherein the firstsilicon germanium material contains a dopant concentration of about2.5×10²¹ atoms/cm³; and exposing the substrate to a second depositiongas comprising dichlorosilane and a germanium source to epitaxially andselectively deposit a second silicon germanium material on thesubstrate.
 2. The method of claim 1, wherein the at least one dopant gasis a boron containing compound selected from the group consisting ofborane, diborane, triborane, trimethylborane, triethylborane, andderivatives thereof.
 3. The method of claim 2, wherein the first silicongermanium material contains a boron concentration of about 2.5×10²¹atoms/cm³.
 4. The method of claim 3, wherein the carbon source is anorganosilane.
 5. The method of claim 4, wherein the carbon source ismethylsilane.
 6. The method of claim 1, wherein the at least one dopantgas includes an arsenic containing compound or a phosphorus containingcompound.
 7. The method of claim 1, wherein the carrier gas is selectedfrom the group consisting of hydrogen, argon, nitrogen, helium, andcombinations thereof.
 8. The method of claim 7, wherein the firstdeposition gas further comprises dichlorosilane.
 9. The method of claim7, wherein the temperature is within a range from about 600° C. to about750° C. and the process chamber is at a pressure within a range fromabout 0.1 Torr to about 200 Torr.
 10. The method of claim 7, wherein thesilicon germanium film has a thickness within a range from about 100 Åto about 3,000 Å.
 11. The method of claim 10, wherein the silicongermanium film is deposited within a device used for CMOS, Bipolar, orBiCMOS application.
 12. The method of claim 11, wherein the silicongermanium film is deposited during a fabrication step selected from thegroup consisting of contact plug, source/drain extension, elevatedsource/drain, and bipolar transistor.
 13. The method of claim 1, whereina silicon-containing material is deposited on the substrate before thefirst silicon germanium material.
 14. The method of claim 13, whereinthe silicon-containing material is deposited by a deposition processcomprising dichlorosilane.
 15. A selective epitaxial method fordepositing a silicon germanium film on a substrate comprising: placing asubstrate within a process chamber; heating the substrate to atemperature within a range from about 500° C. to about 900° C.; andexposing the substrate to a deposition gas comprising silane, agermanium source, a carbon source, an etchant source, a carrier gas, andat least one dopant gas to epitaxially and selectively form a silicongermanium material containing a dopant concentration of about 2.5×10²¹atoms/cm³.
 16. The method of claim 15, wherein the germanium source isselected from the group consisting of germane, digermane, trigermane,tetragermane, and derivatives thereof.
 17. The method of claim 16,wherein the carrier gas is selected from the group consisting ofhydrogen, argon, nitrogen, helium, and combinations thereof.
 18. Themethod of claim 17, wherein the temperature is within a range from about600° C. to about 750° C. and the process chamber is at a pressure withina range from about 0.1 Torr to about 200 Torr.
 19. The method of claim18, wherein the etchant source is selected from the group consisting ofhydrogen chloride, tetrachlorosilane, tetrachloromethane,dichloromethane, chlorine, derivatives thereof, and combinationsthereof.
 20. The method of claim 15, wherein the at least one dopant gasis a boron containing compound selected from the group consisting ofborane, diborane, triborane, trimethylborane, triethylborane, andderivatives thereof.
 21. The method of claim 20, wherein the carbonsource is an organosilane.
 22. The method of claim 21, wherein thecarbon source is methylsilane.
 23. The method of claim 15, wherein theat least one dopant gas is selected from the group consisting of anarsenic containing compound and a phosphorus containing compound. 24.The method of claim 15, wherein the deposition gas further comprisesdichlorosilane.
 25. The method of claim 18, wherein the silicongermanium film has a thickness within a range from about 100 Å to about3,000 Å.
 26. The method of claim 25, wherein the silicon germanium filmis deposited within a device used for CMOS, Bipolar, or BiCMOSapplication.
 27. The method of claim 26, wherein the silicon germaniumfilm is deposited during a fabrication step selected from the groupconsisting of contact plug, source/drain extension, elevatedsource/drain, and bipolar transistor.
 28. The method of claim 15,wherein the silicon germanium material is deposited having a firstthickness, thereafter, the silane is replaced by dichlorosilane, and asecond silicon germanium material is epitaxially and selectivelydeposited having a second thickness on the silicon germanium material.29. The method of claim 15, wherein a silicon-containing material isdeposited on the substrate before the silicon germanium material. 30.The method of claim 29, wherein the silicon-containing material isdeposited by a deposition process comprising dichlorosilane.
 31. Amethod for depositing a silicon germanium film on a substratecomprising: placing a substrate within a process chamber; heating thesubstrate to a temperature within a range from about 500° C. to about900° C.; and exposing the substrate to a deposition gas comprising asilicon-containing gas, a germanium source, a carbon source, hydrogenchloride, and a boron-containing dopant gas to epitaxially andselectively deposit a silicon germanium material on the substrate,wherein the silicon germanium material contains a boron concentration ofabout 2.5×10²¹ atoms/cm³.
 32. A method for depositing a silicongermanium film on a substrate comprising: placing a substrate within aprocess chamber; exposing the substrate to a first deposition gascomprising silane, a first germanium source, a carbon source, hydrogenchloride, and a carrier gas to epitaxially deposit a first silicongermanium containing material having a first thickness on the substrateand containing a dopant concentration of about 2.5×10²¹ atoms/cm³; andexposing the substrate to a second deposition gas comprisingdichlorosilane and a second germanium source to epitaxially deposit asecond silicon germanium containing material having a second thicknesson the first silicon germanium containing material.
 33. The method ofclaim 32, wherein the first silicon germanium containing material isselectively deposited on the substrate.
 34. The method of claim 33,wherein the first deposition gas further comprises at least one dopantgas.
 35. The method of claim 34, wherein the at least one dopant gascomprises an element selected from the group consisting boron, arsenic,phosphorus, and combinations thereof.
 36. The method of claim 35,wherein the at least one dopant gas comprises a boron containingcompound selected from the group consisting of borane, diborane,triborane, trimethylborane, triethylborane, and derivatives thereof. 37.The method of claim 36, wherein the carbon source is an organosilane.38. The method of claim 37, wherein the carbon source is methylsilane.39. The method of claim 33, wherein the second silicon germaniumcontaining material is selectively deposited on the substrate.
 40. Themethod of claim 39, wherein the second deposition gas further compriseshydrogen chloride and at least one dopant gas.
 41. The method of claim40, wherein the at least one dopant gas comprises an element selectedfrom the group consisting boron, arsenic, phosphorus, and combinationsthereof.
 42. The method of claim 41, wherein the at least one dopant gascomprises a boron containing compound selected from the group consistingof borane, diborane, triborane, trimethylborane, triethylborane, andderivatives thereof.
 43. The method of claim 33, wherein the first andsecond germanium sources are independently selected from the groupconsisting of germane, digermane, trigermane, tetragermane, andderivatives thereof.
 44. The method of claim 43, wherein the first andsecond thicknesses are independently within a range from about 100 Å toabout 3,000 Å.
 45. The method of claim 44, wherein the substrate isheated to a first temperature during the exposure of the firstdeposition gas and to a second temperature during the exposure of thesecond deposition gas, wherein the first and second temperatures areindependently a temperature within a range from about 500° C. to about900° C.